The proposed project concerns the elucidation of the factors effecting the rise in serum unconjugated bilirubin and various disorders of the liver in man and characterization of the fetal and neonatal development of the mechanisms involved in hepatic bilirubin transport. Studies on the pathogenesis of jaundice in neonates with congenital gastrointestinal obstruction will consist of direct measurement of uridine diphosphate glucuronyl transferase and uridine diphosphate glucose dehydrogenase in surgical liver biopsies obtained primarily for diagnostic purposes. The effect of alcohol and phenobarbital administration on hepatic glucuronyl transferase and uridine diphosphate glucose dehydrogenase in patients with Gilbert's syndrome will be studied. To further elucidate the effect of caloric intake on the serum unconjugated bilirubin concentration, effect of changes in dietary components on the serum bilirubin in patients with Gilbert's syndrome will be studied. To determine whether the exaggerated increase in serum unconjugated bilirubin, occurring after fasting in patients with Gilbert's syndrome, is related to the increased pre-fasting bilirubin level, the effect of caloric restriction on the serum bilirubin concentration will be studied in a group of patients with hemolytic jaundice.